The present invention relates to an engine starter motor for an internal combustion engine and, particularly, a pinion stopper for the engine starter motor.
An example of a conventional pinion stopper is shown in Japanese Utility Model Publication No. 53727/1980 in which an output shaft which is rotated by a rotation of an armature of the motor is formed in a stepped portion thereof with a helical spline composed of mounting grooves and stopper grooves which are arranged in parallel and alternatively with respect to the mounting grooves. The stopper grooves are terminated at an axial position remote from an end of the output shaft so that they become effective only when a pinion is driven. Lands of spline on the side of an over-running clutch correspond in number to the mounting grooves and a dedendum circle of the spline has a diameter larger than that of the output shaft. When an over running clutch thrust mounted movably on the output shaft is moved axially until it is disengaged from the spline and returned to an original position after it is rotated by one pitch, a spline lands formed on an inner periphery of the thrust becomes coincident in position with the stopper grooves of the herical spline, so that they can be meshed when the thrust is moved forwardly. As means for preventing the thrust spline from escaping rearwardly to the side of the armature motor and for limiting a rearward movement of the thrust spline, a stopper ring is mounted on the output shaft.
With such construction, in order to make the stopper grooves of the helical spline formed on the output shaft coincident with the lands of the thrust spline, it is necessary to rotate the over running clutch thrust spline. Therefore, it is necessary to provide a relief space on the side of the output shaft which is large enough to allow such rotation of the thrust spline and to provide another stopper ring for preventing the thrust spline from dropping out rearwardly after the positional matching between the lands of the thrust spline and the stopper grooves of the helical spline is obtained. The provision of such relief space leads to an undesired increase of overall length of the device.
An object of the present invention is to provide a pinion stopper by which an axial length of a starting motor can be minimized.